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Commercial synthetic fibers of below 10μm in diameter are usually unachievable with conventional melt spinning technology using high molecular weight polymers as the starting materials. The electrospinning process is capable of nanoscale fiber forming but is usually accompanied by the use of 80-90 wt% organic solvents, which greatly reduces the fiber yield and increases process cost as well as causing environmental concerns. We describe herein an approach using the caprolactam monomer as the main starting material for reactive anionic polymerization, propagating the degree of polymerization to achieve suitable melt viscosity for drawing into ultra-fine fibers by the electrostatic field force. The process temperature was well below that of the Nylon 6 melting point. We demonstrate that through this low energy consumption integrated process, essentially all monomers can be transformed into the final Nylon-6 micro/nano fiber assemblies which was unattainable from prior industrial or research processes.

Selective production of glucose from the hydrolysis of cellulose is the key step for efficient utilization of lignocellulose biomass. Crystalline cellulose can be dissolved and hydrolyzed into glucose with a high selectivity in molten salt hydrates (MSHs). However, the separation of the formed glucose is challenging due to its high solubility in the MSHs. To address this issue, a stepwise method is introduced, where cellulose is hydrolyzed into short-chain glucan oligomers in the MSH of LiBr. We demonstrate that compared to glucose, the formed glucan oligomers with a degree of polymerization of 4–11 can be efficiently separated from the MSH hydrolysate using an anti-solvent precipitation method. The separated oligomers can be readily converted into glucose under mild conditions and used for other applications. Under optimized conditions, 90.3% of glucan oligomer can be produced from crystalline cellulose and separated from the MSH with the addition of methanol, and the precipitated glucan oligomer can be hydrolyzed into glucose with a yield of 99.7% using dilute sulfuric acid. We show that the precipitation efficiency is influenced by the glucan oligomer chain length, glycoside bond type and concentration. Moreover, the separation of a glucan oligomer from a cotton straw hydrolysate was also investigated in the MSH. 79.2% yield of glucan oligomer was obtained from the hydrolysis of cotton straw at 130 °C for 2 h. With the addition of methanol, the glucan oligomer was precipitated with a selectivity of 60.8%.

ABA triblock copolymer nanoparticles of poly(2-hydroxypropyl methacrylate)-block-polystyrene-block-poly(2-hydroxypropyl methacrylate) (PHPMA-b-PS-b-PHPMA) with a hydrophobic core of the polystyrene (PS) block and a hydrophilic corona of the poly(2-hydroxypropyl methacrylate) (PHPMA) block were synthesized by dispersion RAFT polymerization. It is found that the particle diameter of the PHPMA-b-PS-b-PHPMA nanoparticles increases with the chain extension of the PS block and decreases with the increasing degree of polymerization (DP) of the PHPMA block. In comparison with the poly(2-hydroxypropyl methacrylate)-block-polystyrene (PHPMA-b-PS) diblock copolymer nanoparticles with a similar chemical composition, the PHPMA-b-PS-b-PHPMA nanoparticles have a larger diameter, and the chain density of the PHPMA chains tethered to the PS core is higher. It is found that the PHPMA-b-PS-b-PHPMA nanoparticles can decrease the n-hexane/water interfacial tension more than the PHPMA-b-PS nanoparticles and may act as an efficient emulsifier.

The RAFT aqueous emulsion polymerization of methyl methacrylate (MMA) is conducted at 70 °C using poly(glycerol monomethacrylate) (PGMA) as a steric stabilizer block. This non-ionic precursor has previously proved to be highly effective for the RAFT aqueous emulsion polymerization of various vinyl monomers such as benzyl methacrylate (BzMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), isopropylideneglycerol monomethacrylate (IPGMA) or glycidyl methacrylate. However, an unexpected constraint was encountered in the case of MMA. Targeting a degree of polymerization (DP) of 20 to 100 for the PMMA block led to colloidal dispersions of kinetically-trapped spherical nanoparticles ranging in size from 17 nm to 31 nm. On the other hand, targeting DPs above 100 invariably led to the formation of highly flocculated spherical nanoparticles. This rather limited DP range is in striking contrast to the much higher DPs that can be targeted without loss of colloidal stability when using more hydrophobic monomers such as BzMA, TFEMA or IPGMA. The same flocculation problem was also evident when employing a PGMA precursor containing an anionic carboxylate end-group, but a series of colloidally stable dispersions could be obtained when using an anionic poly(methacrylic acid) stabilizer. Finally, the efficient removal of RAFT end-groups from PGMA50-PMMA80 nanoparticles was achieved by visible light irradiation using a blue LED source (λ = 405 nm). UV GPC studies confirmed that up to 87% dithiobenzoate end-groups can be removed from such nanoparticles within 12 h at 80 °C. On the other hand, using excess H2O2 under the same conditions only led to 24% end-group removal. This is because this water-soluble reagent has restricted access to the hydrophobic PMMA cores.

The choice of chain transfer agent in reversible addition/fragmentation chain transfer polymerization has proven to be instrumental in modulating the dispersity of a certain polyphenyl vinyl ketone (PVK). The monomer, PVK, which can self-initiate when exposed to blue light, was used to synthesize homopolymers, block copolymers by extending with a different monomer and gradient polymers. Regardless of the polymer architecture or degree of polymerization, a consistent trend in polymer dispersity was quantified, with higher loadings of the less active chain transfer agent xanthate leading to higher dispersities. The dispersity could be further modulated by photodegradation of vinyl ketone polymers under UV irradiation.

Amphiphilic homopolymers are gaining importance due to their easy synthesis compared to copolymers and their ability to assemble into various nanostructures. The majority of reported amphiphilic homopolymers have a non-biodegradable backbone, are charged, and are dependent on pH for assembly. In this work, we report the self-assembly behavior of non-ionic amphiphilic poly(γ-oligo(ethylene glycol)-e-caprolactone) homopolymers (PMExCL, x = 2, 3, and 4), and a novel poly(N-dodecyl-N-(2-(2-(2-methoxyethoxy)ethoxy)ethyl)-7-oxoxepane-4-carboxamide (PME3DDCL) homopolymer. These synthesized amphiphilic homopolymers readily self-assembled forming micelles in a polar environment. PMExCL also exhibited thermoresponsivity; hence, several parameters that affect the thermoresponsivity of these polymers were studied, such as degree of polymerization, concentration, heating rate, and length of oligo(ethylene glycol) side chains. The size, morphology, and thermodynamic stability were investigated, and the micelles were loaded with eugenol to explore the possibility of using the micelles for drug encapsulation. These self-assembled homopolymers hold promise for vast applications, particularly in the biomedical field.

The impact of brush molecular weight distribution on the conformation and response of weak polyacid brushes was investigated. We show that weight-average degree of polymerization (Nw) and dispersity (Đ) alter the pH-responsive conformation of poly(acrylic acid) (PAA) brushes grafted to silica nanoparticles. We quantified the average brush length (lb) at various pH using dynamic light scattering. The lb of low-Nw PAA brushes (Nw = 45) increased as Đ was increased from 1.09 to 1.69, but lb for the high-Nw PAA brushes (Nw ≈ 813) did not vary substantially when Đ was increased from 1.23 to 1.76. This result indicates that the presence of a small fraction of long chains in a broad dispersity brush has a greater impact on lb when Nw is low. Additionally, the extent of pH-response in lb/lb,max increased with Nw or Đ (when Nw is low), where the maximum brush length (lb,max) was lb measured at pH 10. The scaling of lb/lb,max with degree of dissociation (α), however, was influenced by Nw but not Đ, indicating the low- and high-Nw PAA brushes were in the quasi-neutral brush (q-NB) and salted brush (SB) regimes, respectively. Differing behaviors in the pH-response and α-response of lb at low Nw arose from subtle differences in dissociation behaviors among brushes of varying Đ. At low Đ, the low-Nw brush adopted a pH-independent extended conformation due to strong excluded volume interactions, whereas the conformation of the high-Nw brush varied from collapsed to stretched with increasing pH arising from electrostatic interactions. At high-Đ, we suggest the brush conformation also varied from collapsed to stretched with increasing pH regardless of Nw.

A germination treatment was explored in this study as a green strategy to reduce the in vitro starch digestibility of cooked quinoa. The alterations of chemical compositions, starch chain-length distributions (CLDs) and rheological characteristics of quinoa flours after the germination treatment were characterized. Results showed that a significant alteration of amylose CLDs and the starch digestibility was observed for cooked quinoa flours after different germination times. By fitting starch digestograms to the logarithm of slop (LOS) plot and the combination of parallel and sequential kinetics model (CPS), two starch digestible fractions with distinct rate constants were identified. Pearson correlation analysis further found that the observed starch digestive characteristics could be largely explained by the alterations of amylose CLDs caused by the germination treatment. More specifically, the rapidly digestible starch fraction mainly consisted of amorphous amylopectin molecules and amylose intermolecular crystallites. On the other hand, the slowly digestible starch fraction was largely formed by intramolecular interactions among amylose short chains (degree of polymerization (DP) < 500). These results suggest that germination may be a promising way to develop cereal products with slower starch digestibility.

The controlled syntheses of glycerol-based polymers, involving poly(glycidol) (PG)-backbones and thermoresponsive oligo(oxyethylene)-side chains, are described. The organocatalytic ring-opening polymerizations of benzyl glycidyl ether (BnGE) were performed to produce poly(benzyl glycidyl ether)s (PBnGEns) in which the degree of polymerization (n) was predetermined, followed by the removal of the inherent protection groups. For these polymerization/deprotection stages, the synthesis of two major types of polymers is emphasized, in which one is “pristine” PG without any specific end-groups (PGn) and the other is the α-end functionalized PG with hydrophobic aliphatic and aromatic groups (R-PGn). The post-modification reactions based on the addition reactions of isocyanate derivatives to the hydroxyl side groups were adopted for PGn and R-PGn, thus producing poly[glycidyl oligo(oxyethylene)carbamate]s with diverse structures. The structures can generally be expressed as PGn-EOmR′ and R-PGn-EOmR′, where (i) the degree of polymerization (n), (ii) the alkyl group at the periphery of the side groups (R′), (iii) the number of oxyethylene chains (m), and (iv) the α-end group (R) can be independently controlled and/or selected. The effects of the parameters/structures (i)–(iv) on the thermoresponsive properties and the supporting data for the phase transitions in aqueous media are described in detail.

Polymerization-induced self-assembly (PISA) is widely recognized to be a powerful technique for the preparation of diblock copolymer nano-objects in various solvents. Herein a highly unusual non-aqueous emulsion polymerization formulation is reported. More specifically, the reversible addition–fragmentation chain transfer (RAFT) polymerization of N-(2-acryloyloxy)ethyl pyrrolidone (NAEP) is conducted in n-dodecane using a poly(stearyl methacrylate) (PSMA) precursor to produce sterically-stabilized spherical nanoparticles at 90 °C. This relatively high polymerization temperature was required to ensure sufficient background solubility for the highly polar NAEP monomer, which is immiscible with the non-polar continuous phase. A relatively long PSMA precursor (mean degree of polymerization, DP = 36) was required to ensure colloidal stability, which meant that only kinetically-trapped spheres could be obtained. Dynamic light scattering (DLS) studies indicated that the resulting PSMA36–PNAEPx (x = 60 to 500) spheres were relatively well-defined (DLS polydispersity

Ring opening polymerization (ROP) is commonly used to synthesize biodegradable polymers such as polycaprolactone (PCL). These reactions typically demand anhydrous reagents and inert atmosphere, only attainable through the use of complex setups including glove boxes and Schlenk lines. Because of these practical limitations, ROP is typically inaccessible to the non-expert. Herein, we have developed two techniques for limited ROP of e-caprolactone (CL) without previous drying of reagents by simply conducting the reaction in a laboratory oven. In the first method, a vacuum oven was used to evaporate water from a traditional ROP reaction with stannous octoate (Sn(Oct)2) as the catalyst. In the second method, we ‘polymerize through’ water using titanium isopropoxide (TTIP) to simultaneously quench residual water and catalyze ROP. Using these two methods, we achieved variable chain length (degree of polymerization (DP) 25–500) and molecular weight distribution (Đ = 1.3–1.5) of PCL. We found that ROP with TTIP works better for higher molecular weights up to DP 500 than Sn(Oct)2 under vacuum. Moreover, we investigated the living nature of ROP with TTIP where a block copolymer of PCL-PLA was achieved.

A method is demonstrated for obtaining high glass transition temperature (Tg) plastically deformable crosslinked polymer systems by manipulating the network topology of epoxy systems cured with amines. Long-chain Monoamine-functionalized Partially Reacted Substructures (mPRS) were synthesized by reacting a mixture of tetraglycidyl ether of diaminodiphenylmethane (TGDDM) and polyether monoamine (PEMA) to varying extents. Predetermined amounts of the mPRS having 0%, 60%, and 80% degree of polymerization were added to a mixture of a TGDDM and polyether diamine (PEDA) as well as a mixture of diglycidyl ether of bisphenol-A (DGEBA) and PEDA. Results of quasi-static tensile tests performed on the cured samples reveal pronounced strain hardening and, subsequent, large elongation-to-failure in the modified epoxy systems containing mPRS with elevated degrees of polymerization. Thus materials with distinctly improved elongation-to-failure are obtained for systems with identical overall chemical composition. The striking difference is attributed to plastic microvoid growth aided by the presence of deformable mPRS domains. Fracture surfaces of deformed mPRS modified systems show the characteristic formation of microvoids. In comparison, similar systems based on less deformable diamine functionalized substructures (PRS), on which we reported previously, did not show the same propensity to yield and deform plastically.

Liposomes are small artificial vesicles spherical shaped of 50–1000 nm in diameter. They are created from natural non-toxic phospholipids membranes. Externally, they are decorated with biocompatible polymers. Chitosan, a natural polymer, demonstrates exceptional advantages in drug delivery, in particular, as liposome cover. In this paper, Molecular Dynamics simulations (MD) are performed in the coupled NPT-NPH and NVT-NVE statistical ensembles to study the static and dynamic properties of DPPC membrane-bilayer with grafted cationic chitosan chains, with added Cl− anions to neutralize the environment, using the Martini coarse-grained force-field. From the NPT-NPH MD simulations we found a chitosan layer LDM ranging from 3.2 to 6.6 nm for graft chains of a degree of polymerization np = 45 and different grafting molar fractions Xp = 0.005, Xp = 0.014 and Xp = 0.1. Also, the chitosan chains showed three essential grafting regimes: mushroom, critic, and brush depending on Xp. The DPPC bilayer thickness DB and the area per lipid Al increased proportionally to Xp. From the NVT-NVE MD simulations, the analysis of the radial distribution function showed that the increase of Xp gives a more close-packed and rigid liposome. The analysis of the mean square displacement revealed that the diffusion of lipids is anomalous. In contrast, the diffusion of chitosan chains showed a normal diffusion, just after 100 ps. The diffusion regime of ions is found to be normal and independent of time. For the three identified regimes, the chitosan showed a tendency to adhere to the membrane surface and therefore affect the properties of the liposomal membrane.

2-Aminoisobutyric acid (Aib) is a prominent achiral amino acid known for its helical building properties, generating left- and right-handed helices without any preference. We here report an investigation on several short chain poly(Aib)s synthesized by ring opening polymerization (ROP) of Aib-N-carboxy-anhydrides (Aib-NCA) with structurally different chiral amines acting as both, initiator and chiral induction agent. To achieve the desired structures with a degree of polymerization of 10 up to 20 repeating units, different synthetic techniques such as solution and interfacial polymerization have been used leading to improved purity and precise end group control of the resulting polymers as confirmed by MALDI-ToF-MS and 1H-NMR spectroscopy. By adding a chiral center at the C-terminus of the polymer chain we can control the direction of the screw sense, since the polymers are adopting the chirality of the initiator following the sergeant-and-soldier principle. Circular-Dichroism (CD) spectroscopy measurements revealed an exceptionally good chiral induction by the investigated initiators. Furthermore, variation of the solvent from hexafluoroisopropanol (HFIP) to water resulted in a significant change of CD signals, featuring a surprising aggregation of the poly(amino acids) into globular aggregates in water in the range of 50 to 200 nm, which accounts for changes in chiral induction.

Fluorinated liquid crystal polymers (FLCPs) with an AB/A2B-alternating sequence of fluorinated biphenyl moieties (FMs) along their backbones were constructed, where the anionic copolymerization of isoprene (Ip) with, mono-SiH and di-SiH functionalized 1,1-diphenylethylene (DPE) derivatives was performed to prepare alternating copolymer precursors with exactly controlled single-site densities of -SiH, i.e., alt-P(D-S/Ip) and alt-P(D-2S/Ip), respectively, followed by highly efficient hydrosilylation to introduce FMs into the repeating unit (DPE). Previous work indicated that the mesogenic properties were related to the distance between neighbouring mesogenic moieties in different polymerized units when the degree of polymerization (DP) of the copolymers was low. Hence, the present strategy provides a novel model to explore dependence of the mesogenic properties on the exactly controlled single-site functionalized density of mesogens (FMs) for the resulting alternating-templated FLCPs, which was achieved due to a quite low DP (11 for mono-SiH and 5 for di-SiH), while exhibiting a similar overall concentration of FMs along backbones bearing a similar number of Si–H groups. The results show that the polarized optical textures and the temperature range of mesogenic phase formation (ΔT) varied remarkably between A2B-alternating (ΔT = 104 °C) and AB-alternating (ΔT = 23 °C) FLCPs; in particular, the variation in phase transition temperature is possibly a result of exactly controlled single-site functionalized density. Herein, a novel morphological aggregation model is proposed to increase the comprehension of how the exactly controlled single-site functionalized density of FMs arranged within the small scale of polymer chains directs molecular packing and interactions between them, thereby enriching the diversity of molecular interactions.

Discrete oligomers are perfect candidates for understanding the structure-dependent properties of polymers. Herein, a series of discrete conjugated oligo(fluorenediacetylene)s (D-oFDAs) with a degree of polymerization (DP) up to 10 were obtained by purification with automated flash column chromatography from polydisperse polymers. It is found that the chain length can affect not only photophysical properties but also crystalline properties. As the DP of D-oFDAs increased, the longer conjugation length caused red shifts in their optical spectra and weaker crystallinity. The effective conjugation length has been extrapolated to be as long as 9 fluorenediacetylene units. Moreover, the oligomers can form uniform films by solution casting for the fabrication of light-emitting diodes, showing that the octamer has the most efficient electroluminescence (EL) properties. When the crystal of the dimer was exposed to 254 nm UV light, only part of the sample was polymerized via a 1,4-addition reaction. Significantly, the simple, scalable and effective strategy provides opportunities to further optimize the structure with diverse blocks and side chains for precisely building macromolecular architectures.

The SG surface was functionalized with dithizone, R@-{SiO2}n, in a single step for selective sample clean-up and preconcentration of Gd(III) amidst Fe(III), Th(IV), and Ce(IV). Exploiting the differences in pH for extraction/or using selective eluents, the analytes were selectively separated. The sorbent brilliantly preconcentrates the dilute solutions of Gd(III), Fe(III), Th(IV), and Ce(IV) with a high level of enrichment factors at 183.2, 184.0, 184.1, and 182.1, respectively. The sorption process was found to be entropy gaining (ΔS: 0.033 ± 0.001 kJ mol−1 K−1), exothermic (ΔH: −0.098 ± 0.007 kJ mol−1), and spontaneous (ΔG: −9.89 ± 0.31 kJ mol−1). Systematic studies ensure the quantitative sorption of Gd(III), Th(IV), and Ce(IV) at their solution pH 5.75–6.5; while that for Fe(III) was found to be pH 2.25 ± 0.25. The hydroxy complexes [Gd2(OH)2(H2O)8]4+, [Fe2(OH)2(H2O)5]4+, [Ce(OH)2(H2O)4]2+ and [Th(OH)2(H2O)14]2+ exist at their respective sorption pH and being present in the vicinity of the electron-enriched ‘extractor-HOMO’ makes 1 : 1 ion-pair complexes, {extractor-HOMO} : {metal-hydroxy species}n+. The maximum sorption capacity (BTC) was determined from BTC = {amount of HOMO (μmol g−1) × x} = 172 × x μmol g−1 (where x, the degree of polymerization of a particular metal ion at its extraction pH is an integer and its numerical value(s) become(s) 2 for Gd(III)–Fe(III) and 1 for Th(IV)–Ce(IV)). The reusability (1600–1800 cycles) and the maximum sorption capacity (337.8, 331.1, 178.0, and 182.5 μmol g−1, respectively, for Gd(III), Fe(III), Th(IV), and Ce(IV)) of the extractor with a durability of 18 months was outstanding.

L-Lactide was polymerized with tin(II)acetate, tin(II)2-ethyl hexanoate, diphenyltin dichloride and dibutyltin bis(pentafluorophenoxide) at 130 °C in bulk. When an alcohol was added as initiator, linear chains free of cycles were formed having a degree of polymerization (DP) according to the lactide/initiator (LA/In) ratio. Analogous polymerizations in the absence of an initiator yielded high molar mass cyclic polylactides. Quite similar results were obtained when e-caprolactone was polymerized with or without initiator. Several transesterification experiments were conducted at 130 °C, either with polylactide or poly(e-caprolactone) indicating that several transesterification mechanisms are operating under conditions that do not include formation of cycles by back-biting. Furthermore, reversible polycondensations (revPOCs) with low or moderate conversions were found that did not involve any kind of cyclization. Therefore, these results demonstrate the existence of revPOCs, which do neither obey the theory of irreversible polycondensation as defined by Flory nor the hypothesis of revPOCs as defined by Jacobson and Stockmayer. A new concept encompassing any kind of revPOCs is formulated in the form of a “polycondensation triangle”.

Two sugar PEG-based amphiphilic copolymers have been synthesized by Novozym®-435-catalyzed greener solvent free transesterification reaction of diastereomeric 2,6-anhydro-3,4,5-tri-O-benzyl-glucoheptitol and 2,6-anhydro-3,4,5-tri-O-benzyl-mannoheptitol with PEG-1000 diethyl ester in 80 and 76% yields, respectively. It has been observed that the configurational change at one of the carbons of diastereomeric 2,6-anhydro-heptitols has significant bearing on the degree of polymerization and characteristics of the synthesized polymers. Thus, the study of physico-chemical characteristics of synthesized anhydroglucoheptitol- and anhydromannoheptitol-PEG copolymers revealed that their aqueous solution forms spherical micelles of hydrodynamic diameters 11.2 and 6.4 nm, respectively. Micelles derived from both the amphiphilic copolymers have the potential to solubilize the hydrophobic dye, Nile red. Furthermore, a fluorescence microscopy study revealed that Nile red encapsulated micelles of synthesized amphiphilic copolymers uniformly internalized in A549 cells and thus can be used as a cargo carrier in biological systems. The viability of A549 cells was found to be very high even at a concentration of 500 μg mL−1 of copolymer indicating that they are cyto-compatible.

A series of poly(stearyl methacrylate)–poly(benzyl methacrylate) (PSMA–PBzMA) diblock copolymer nano-objects has been synthesized via reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization in n-dodecane at 20 wt. %. This polymerization-induced self-assembly (PISA) formulation was modified by the incorporation of an anionic monomer, tetradodecylammonium 3-sulfopropyl methacrylate ([NDod4]+[SPMA]-) into the oil-insoluble PBzMA block. According to the literature (M. J. Derry et al., Chem. Sci., 2016, 7, 5078–5090), PSMA18–PBzMA diblock copolymers only form spheres using this formulation for any core DP. Unexpectedly, incorporating just a small fraction (4]+[SPMA]- comonomer into the structure-directing block resulted in the formation of non-spherical diblock copolymer nano-objects, including pure worm-like and vesicular morphologies. However, only spherical micelles could be formed using a longer PSMA34 stabilizer. These diblock copolymer nano-objects were characterized by transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. The bulky nature of the ionic comonomer appears to make it possible to avoid the kinetically-trapped sphere morphology. This study reveals a new approach for tuning the morphology of diblock copolymer nano-objects in non-polar media.

Epoxy-functional diblock copolymer spheres, worms and vesicles are synthesized at 30% w/w solids via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of glycidyl methacrylate (GlyMA) in mineral oil at 70 °C. This is achieved by using a relatively short oil-soluble poly(stearyl methacrylate) (PSMA) macromolecular chain transfer agent (macro-CTA) with a mean degree of polymerization of 9. Gel permeation chromatography (GPC) studies indicate that good control over the molecular weight distribution can be obtained and the resulting PSMA9-PGlyMAx nano-objects are characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Oscillatory rheology studies of a 30% w/w PSMA9-PGlyMA75 worm gel indicate that thermally-triggered degelation occurs on heating to 100 °C. TEM studies indicate that a partial worm-to-vesicle transition occurs under such conditions.

In this study, the synthesis of small molecules and use of an improved “one-pot” method to synthesize the reversible addition–fragmentation chain transfer polymerization (RAFT) reagents have been reported. By comparing with the RAFT reagents synthesized by the traditional “step-by-step” method, it was observed that the reagents synthesized by the two methods had the same structure, however, the improved “one-pot” preparation method results in a significantly higher yield. Subsequently, two different macromolecular CTA segments (PVP-CTA-PVP and PDMAEMA-CTA-PDMAEMA) were prepared by RAFT polymerization, followed by the synthesis of the block polymer PDMAEMA-b-PVP-CTA-PVP-b-PDMAEMA. Through FITR, NMR, GPC and DLS analysis of the block polymer, it was observed that the isotacticity gradually became dominant as the degree of polymerization increased. Further, using NMR spectroscopy to study the effect of pH on the block polymer, the ionization degree of the synthesized polymer in the tumor tissue environment was observed to range between 86.32% to 99.50%, which proved that the synthesized polymers exhibit significant prospects in the medical application.

We report a new method of determining the chain transfer constant in free radical polymerization using molecular weight distribution data. It is specifically designed for systems where its value is substantially greater than 1. In these cases the classical Mayo equation and Gilbert's chain length distribution (CLD) method fall short, in that the concentration ratio of chain transfer agent to monomer can no longer be assumed to be constant. Marked composition drift invalidates the use of both. In our proposed method we use the analytical concentration ratio of chain transfer agent to monomer (t = 0 s) and monomer conversion data, in combination with data for the cumulative molecular weight distributions as input. We determined an analytical solution for the cumulative weight distribution, which is used to calculate the cumulative number and chain length distributions. Chain transfer constants are found either by fitting the natural logarithmic chain length distribution (CLD) data at a given monomer conversion, or by plotting the fitted values for the slopes obtained from the natural logarithmic chain length distribution (CLD) data at a set degree of polymerization, as a function of monomer conversion. Our method is validated by analyses of molecular weight data obtained from Monte Carlo simulations. We used our methodology to determine an experimental value of ca. 223 as a chain transfer constant of n-dodecanethiol in vinyl acetate free radical polymerization at 333.15 K, which we showed was in excellent agreement with the Smith method.

Modified chitosan (CS) has kindled considerable research interest in the last few decades due to its outstanding biological, chemical and physical properties. Generally, CS can be re-formed with different structural modifications by using various functional groups. Due to the addition of these functional groups, the physicochemical properties of CS can be enhanced without hampering the degree of polymerization inherent in the CS. Different techniques were employed for the modification of CS. Among these, modifications via reversible-deactivation radical polymerization (RDRP) are found to be the most efficient. RDRP techniques mostly include atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer polymerization (RAFT) and nitroxide-mediated polymerization (NMP). These methods provide tailored modifications of CS with controlled molecular weight and dispersity (Đ) leading to better mechanical properties compared to the modifications performed via conventional methods. Various analytical techniques such as FT-IR, UV-Vis, 1H-NMR, 13C-NMR, XRD, SEM, TEM, TGA, DSC, GPC, etc. are employed to characterize and elucidate the physico-chemical properties of these modified polymers. These modifications make CS a strong candidate for different applications in diverse fields of pharmaceuticals, biomedicine, water treatment, etc. This review covers the recent advances in the syntheses, properties and applications of modified CS via RDRP techniques.

Certain block copolymer assemblies in selective solvents undergo dynamic morphology transitions (metamorphism) on varying the solution temperature. Despite the great application potential, there is a lack of fundamental understanding of the relationship between copolymer composition and the thermally-induced metamorphic behavior. Herein this relationship is studied by applying Scheutjens-Fleer Self-Consistent Field (SF-SCF) theory to develop fundamental design principles for thermoresponsive diblock copolymers exhibiting metamorphic behavior. It is found that metamorphism is caused by variation in the degree of stretching of the lyophobic blocks in response to changes in solvency. An optimal lyophobic/lyophilic block length ratio interval 3.5 ≲ fB ≲ 5.5 is identified. Such a fB window allows switching between spheres, cylinders and vesicles as preferred morphologies, with relatively small changes in the lyophobic block solvency. The transition from spheres to cylinders and from cylinders to bilayers can be controlled by varying fB, the overall degree of polymerization of the diblock copolymer, and by choosing an appropriate lyophilic block. Empirical relationships are provided to establish a connection between the SCF-SCF predictions and experimental observations.

Salt-containing supramolecular assemblies of rigid-rod polymers tethered with flexible ion-solvating side chains represent a synthetic pathway towards thin ion-conducting solid electrolyte membranes with high dimensional stability. In the present work we have synthesized poly(p-phenylene)s (PpPs) carrying di-, tri- and tetra(ethylene oxide) side chains, respectively. p-Dichlorophenyl oligo(ethylene oxide) monomers were polymerized by Ni-mediated Yamamoto polymerization via in situ reduction of Ni(II). This gave PpPs with an average degree of polymerization reaching 60, where each phenylene ring carried one oligo(ethylene oxide) side chain. Results from calorimetry and X-ray scattering measurements clearly showed the formation of molecular composites, i.e., bicontinuous morphologies with mechanically reinforcing layers of the stiff PpP backbones separated by the flexible oligo(ethylene oxide) side chains. This morphology was retained after adding lithium bis(trifluoromethane)sulfonimide (LiTFSI) to form salt-in-polymer electrolytes, but with an increased distance between adjacent backbones. Furthermore, upon addition of salt the order-to-disorder transition (ODT) region increased from ∼50–170 °C to ∼75–200 °C at [EO]/[Li] = 20. Increasing salt concentrations also revealed a maximum in the ODT enthalpy at [EO]/[Li] = 40. At 80 and 160 °C, the ionic conductivity reached 1.1 × 10−4 and 1.0 × 10−3 S cm−1, respectively. Finally, we demonstrate that ionic conductivity of the polymer electrolytes can be significantly increased by additions of triglyme.

Mother Nature produces a perfectly defined architecture that inspires researchers to make polymeric macromolecules for an array of functions. Preparation of a pre-defined polymer architecture is a key challenge to a researcher. The present article describes the recent development in Polymerization Induced Self-Assembly (PISA) to synthesize polymeric nanoparticles with pre-defined morphology and precise control over size and shape. This methodology has become a potential strategy for the synthesis of various block copolymer nano-objects. The PISA strategy produces core–shell polymeric nanoparticles with a wide scope of morphologies including spheres, worms, rods, and vesicles. A few parameters including the degree of polymerization, core-forming monomers, macro-CTA and solid content of the final product are precisely employed for the PISA procedure to accomplish the ideal size and shape. PISA opens a new avenue for the production of polymeric nano-objects.

Poly(stearyl methacrylate)-poly(2-hydroxypropyl methacrylate) (PSMA-PHPMA) diblock copolymer nanoparticles are synthesized via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) in mineral oil at 90 °C. The relatively short PSMA precursor (mean degree of polymerization = 9) remains soluble in mineral oil, whereas the growing PHPMA block quickly becomes insoluble, resulting in polymerization-induced self-assembly (PISA). Relatively high HPMA monomer conversions (≥98%) were achieved within 70 min as confirmed by in situ1H NMR spectroscopy studies, while gel permeation chromatography (GPC) analyses indicated high blocking efficiencies and relatively narrow molecular weight distributions (Mw/Mn ≤ 1.37) for all PISA syntheses. Depending on the precise synthesis conditions, this PISA formulation can produce diblock copolymer spheres, worms or vesicles; a pseudo-phase diagram has been constructed to enable reproducible targeting of each pure phase. Thus this is a rare example of the use of a commercially available polar monomer for PISA syntheses in non-polar media that offers access to the full range of copolymer morphologies. The resulting nanoparticles were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), oscillatory rheology and small-angle X-ray scattering (SAXS). Interestingly, PSMA9-PHPMA70 worms undergo an unusual (partial) worm-to-vesicle transition at elevated temperature. Finally, PSMA9-PHPMA50 spheres were evaluated as putative Pickering emulsifiers. Using lower water volume fractions produced water-in-oil (w/o) emulsions after high shear homogenization, as expected. However, using higher water volume fractions, shear rates or copolymer concentrations favored the formation of w/o/w Pickering double emulsions.

Sequence-controlled copolymers have recently attracted great interest in a variety of applications, including antimicrobial materials. However, owing to the nature of radical polymerization, targeting multiblocks with low degree of polymerization is complicated due to the possibility of defective chains, significantly affecting the purity of the targeted materials. In addition, the effect of optimum DP and defective chains on the antimicrobial properties of sequence-controlled copolymers remains elusive. Herein, we report the quantitative synthesis of low molecular weight copolymers via photo-induced ATRP aiming to identify the influence of degree of polymerization, block order and the defects on antimicrobial properties of sequence-controlled materials. We demonstrate that sequence-controlled copolymers with shorter amine blocks increase the antimicrobial efficacy of the resulting material towards Gram-negative bacteria while shorter hydrophobic blocks improve the efficacy towards Gram-positive bacteria. Importantly, we also demonstrate that sequence-controlled materials with very low degree of polymerization (DP = 3) exhibit the highest antimicrobial activity, despite the presence of defective chains. This work offers new insights into the structure/property relationship and highlights the promise of low DP, sequence-controlled block copolymers prepared by controlled polymerizations.

A monohydroxy-capped hydrogenated polybutadiene (PhBD) is converted into a macromolecular chain transfer agent via esterification using a carboxylic acid-functionalized trithiocarbonate. 1H NMR and UV spectroscopy studies indicated a mean degree of esterification of at least 95%. The resulting precursor is used for the reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) in n-dodecane at 90 °C. In principle, systematic variation of the mean degree of polymerization (DP) of the insoluble structure-directing PBzMA block should enable the formation of PhBD–PBzMA spheres, worms or vesicles via polymerization-induced self-assembly (PISA). In practice, only kinetically-trapped spheres are obtained when targeting DPs of up to 300 at 25% w/w solids. However, increasing the copolymer concentration up to 40% or 45% w/w provides access to well-defined worms or vesicles, respectively. Gel permeation chromatography and 1H NMR spectroscopy studies confirmed relatively narrow molecular weight distributions (Mw/Mn < 1.20) and high final BzMA conversions (≥99%), respectively. These diblock copolymer nano-objects were characterized in terms of their particle size and morphology using TEM and DLS and a phase diagram was constructed. According to rheology studies, the free-standing worm gels that are formed at ambient temperature have a critical gelation concentration of approximately 5.0% w/w.

A deep eutectic solvent (DES) based on choline chloride and imidazole (CCIMI) was investigated for swelling of cellulose fibers prior to mechanical disintegration into cellulose nanofibers (CNFs). The dimensions of the DES treated and washed fibers were investigated after various treatment conditions (time, temperature, and cellulose consistency) using DES based on choline chloride–urea (CCUrea) and pure imidazole as references. Even mild treatment conditions (15 minutes at 60 °C) with CCIMI increased the diameter of the fibers from 18.1 to 18.9 μm, and a maximum diameter of 19.9 μm was obtained after three hours at 100 °C. Overall, CCIMI resulted in a higher degree of swelling compared to both references. In addition, pure imidazole caused a decrease in the degree of polymerization of cellulose, whereas cellulose degradation in CCIMI was negligible. The mechanical disintegration of CCIMI-treated fibers resulted in the production of CNF films with very good mechanical properties—specific tensile strength and work capacity being over 200 kNm kg−1 and 10 kJ kg−1, respectively—whereas CNFs films produced using choline chloride–urea had notably lower values (182 kNM kg−1 and 7 kJ kg−1, respectively). In addition, CNF films exhibited good oxygen barrier properties, even at an elevated relative humidity level (80%). CCIMI could be recycled without any effect on the mechanical properties of CNF films. The results presented here indicate CCIMI is a highly efficient pretreatment media for swelling and further nanofibrillation of cellulose, even at mild treatment conditions.

Bioinspired polypeptoids show great potential in many applications. Here, we report a convenient approach to synthesize a novel type of polypeptoid containing both sulfonium and oligo(ethylene glycol) (OEG) moieties by ring-opening polymerization (ROP) and a post-modification strategy. Three types of epoxides with (OEG)n (n = 1-3) groups are involved to offer various functionalities. The obtained polypeptoid sulfonium salts show positive ζ potential, irrespective of the solution pH and the degree of polymerization (DP). We demonstrate that the polypeptoids exhibit excellent antibacterial activity against Staphylococcus aureus (S. aureus) with MIC (minimal inhibitory concentration) in the range of 3.9-7.8 μg mL-1. In addition, the polypeptoids have a low hemolysis property and good in vitro biocompatibility. Remarkably, the as-prepared polypeptoids show rapid and potent antibacterial activity within 5 min. These features suggest that the obtained polypeptoids offer great potential for antimicrobial agents.

Low dispersity poly(methyl acrylate) with a target degree of polymerization of 10 (poly(MA)10) was produced in both batch and a continuous tubular reactor at room temperature using Cu(0) catalysis. The resulting polymer solution could be stored for over a week while maintaining excellent activity as a macroinitiator for the further growth of poly(acrylate) chains in both batch and semi-batch reactor systems. The chain-extensions were done without addition of further copper to the system using ascorbic acid as a reducing agent; the best performance (>90% conversion with excellent control) was achieved when a fraction of the ascorbic acid was added to the reactor at the start of reaction, with the rest fed in a semi-batch fashion along with monomer over three hours. Semi-batch chain extensions of poly(MA)10 with butyl acrylate and poly(ethylene glycol) methyl ether acrylate (PEGMEA) were conducted, and a tri-block polymer was also synthesized. The feasibility of applying this procedure to other monomers was demonstrated through the synthesis and chain extension of poly(PEGMEA)10. The combination of the tubular reactor to produce macroinitiator and subsequent semi-batch chain extension is proposed as a versatile process to efficiently produce block copolymers at an industrial scale.

The degree of polymerization and temperature dependencies of the molecular motions, configuration and hydration behaviour of glucose oligomers (Gn, n = 2 to 7, degree of polymerization) in aqueous solutions were investigated using extremely high-frequency dielectric spectrum measuring techniques up to 50 GHz. The obtained dielectric spectra for the aqueous Gn solutions were well decomposed into four Debye-type relaxation modes. The fastest relaxation mode j = 1 was assigned to the rotational process of free water molecules in the sample solution. The second fastest mode j = 2 was attributed to the exchange process of hydrated water molecules with free water molecules, and the third mode j = 3 was recognized as the rotational process of hydroxy groups attached to each repeating glucopyranoside (Glu) unit after their lifetimes of intramolecular hydrogen bonding. The slowest mode j = 4 at a relaxation time depending on n was assigned to the overall rotation of the Gn molecules possessing configurations similar to that of small fragments of single helical V-type crystalline structures at low temperatures. The presence of the dielectric mode j = 4 revealed that the Glu units possessed electric dipole moments carrying a component parallel to the Gn backbone aligned with the C1 → C4 direction. The number of hydrated water molecules per Glu unit (hydration number, nH) was determined for Gns in aqueous solutions in the temperature range from 10 °C to 70 °C via the relaxation strength of mode j = 1. The Gn oligomers were highly soluble in water within the temperature range examined, possessing nH values slightly dependent on n and demonstrated clear dehydration behaviour at approximately 30 °C with increasing temperature. These temperature dependencies of nH were substantially weaker than those of a model Glu unit compound, methyl α-D-glucopyranoside (G1). Then, the polymerization of glucose oligomers effectively depresses the dehydration behaviour of G1.

Regioselective addition of nonsymmetrical monomers in radical polymerization is a basic issue for control of the kinetics and structure of the resulting products. In RAFT polymerization, head addition generates primary alkyl adducts trapped by RAFT agents. Due to the low leaving ability of primary alkyl radicals, this kind of adduct in RAFT polymerization will become non-active macro-RAFT agents, i.e., dead dormant species (DDS). The contents of non-active macro-RAFT agents in RAFT polymerization of three acrylates (ethyl, butyl, and 2-ethylhexanyl acrylate), two methacrylates (ethyl and butyl methacrylate) and styrene were determined by a combination technology of RAFT block polymerization derivation and gradient polymer elution chromatography. The head addition incidences of these monomers were estimated according to our previously proposed formula between the DDS content and head addition incidence. The results showed that the number or type of side chains both had significant influence on head addition incidence, with incidence of methacrylates and styrene about one order of magnitude smaller than that of acrylates due to steric repulsion effects. The results also showed that DDS contents would accumulate with increased degree of polymerization. Therefore, head addition played an important role in acrylate RAFT polymerization when product composition was considered, especially for polymers of high molecular weight.

A visible light and temperature responsive diblock copolymer of poly[6-(2,6,2′,6′-tetramethoxy-4′-oxyazobenzene) hexyl methacrylate]-block-poly(N-isopropylacrylamide) (PmAzo-b-PNIPAM) was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization by carefully tuning the polymerization conditions. The PmAzo-b-PNIPAM block copolymer forms micelles in water, and the hydrophobic and visible light responsive PmAzo block forms the core of the micelles and the thermoresponsive PNIPAM block keeps the micelles suspended in water. The size of the micelles is firmly correlative with the degree of polymerization (DP) of the PmAzo and PNIPAM blocks. The PmAzo-b-PNIPAM micelles are thermo-responsive and photo-responsive. Aggregation of micelles occurs at temperature above the phase transition temperature of the PNIPAM block, which slightly decreases with the DP of the PmAzo block. The visible-light-induced isomerization of the azobenzene moieties in the PmAzo block leads to a decrease or increase of the hydrodynamic diameter Dh of the micelles depending on the irradiation light wavelength.

Recent progress on stretchable, tough dual-dynamic polymer single networks (SN) and interpenetrated networks (IPN) has broadened the potential applications of dynamic polymers. However, the impact of macromolecular structure on the material mechanics remains poorly understood. Here, rapidly exchanging hydrogen bonds and thermoresponsive Diels–Alder bonds were included into molecularly engineered interpenetrated network materials. RAFT polymerization was used to make well-defined polymers with control over macromolecular architecture. The IPN materials were assessed by gel permeation chromatography, differential scanning calorimetry, tensile testing and rheology. The mechanical properties of these IPN materials can be tuned by varying the crosslinker content and chain length. All materials are elastic and have dynamic behavior at both ambient temperature and elevated temperature (90 °C), owing to the presence of the dual dynamic noncovalent and covalent bonds. 100% self-healing recovery was achieved and a maximum stress level of up to 6 MPa was obtained. The data suggested the material's healing properties are inversely proportional to the content of the crosslinker or the degree of polymerization at both room and elevated temperature. The thermoresponsive crosslinker restricted deformation to some extent in an ambient environment but gave excellent malleability upon heating. The underlying mechanism was explored by the computational simulations. Furthermore, a single network material with the same crosslinker content and degree of polymerization as the IPN was made. The SN was substantially weaker than the comparable IPN material.

Polymer self-assembly was utilized in changing the morphology of polymers in both solution and bulk. Therefore, the physical properties of the polymers were changed for special applications. Herein, we study the effect of self-assembly on the magnetic properties of inorganic/organic hybrid magnetic polymers. In detail, three different molecular weight magnetic polymers based on polyhedral oligomeric silsesquioxane (POSS) and pyridinium FeCl4 (POSS-QP4VP[FeCl4]-3k, POSS-QP4VP[FeCl4]-6k, and POSS-QP4VP[FeCl4]-9k) were designed and synthesized by the post-modification of POSS-QP4VP, which were prepared by RAFT polymerization. The prepared polymers showed paramagnetic properties at 300 K and their magnetic susceptibility increased with the degree of polymerization. In a selective solvent, the polymers self-assembled into spheres with POSS aggregates as the core and QP4VP[FeCl4] as the shell, and the thickness of the shell increased with increasing molecular weight. The magnetic properties were affected by self-assembly and molecular weight. For those with a molecular weight of 3k, the magnetic susceptibility was greatly increased. However for those with molecular weights of 6k and 9k, the magnetic susceptibility was decreased. The magnetic susceptibility was closely related to the surface packing of QP4VP[FeCl4] chains, which were more amorphous at a higher molecular weight.

Well-defined multi-arm star thermoresponsive block copolymer nano-assemblies of [poly(N-isopropylacrylamide)-block-polystyrene]n [(PNIPAM-b-PS)n] with n = 1, 2, 3 and 4 arms were synthesized by RAFT dispersion polymerization via polymerization-induced self-assembly. By carefully changing the degree of polymerization (DP) of the polystyrene (PS) block and modulating the polymerization conditions, (PNIPAM-b-PS)n nano-assemblies with similar DP and similar chain density but different topology structures of the tethered poly(N-isopropylacrylamide) (PNIPAM) chains were obtained. By comparatively studying the thermoresponse via turbidity analysis, dynamic light scattering, variable-temperature 1H NMR and rheological analysis, it was found that the phase transition temperature of the tethered PNIPAM chains in the (PNIPAM-b-PS)n nano-assemblies correlates to the number of arms, n, demonstrating that the topology of the tethered PNIPAM chains exerts a significant influence on the thermoresponsive phase transition.

Traditionally, post-polymerization processing routes have been used to obtain a wide range of block copolymer morphologies. However, this self-assembly approach is normally performed at rather low copolymer concentration, which precludes many potential applications. Herein, we report a facile method for the preparation of block copolymer particles exhibiting complex internal morphology via polymerization-induced self-assembly (PISA). More specifically, a series of diblock copolymers were synthesized by reversible addition–fragmentation chain transfer (RAFT) alternating copolymerization of styrene (St) with N-phenylmaleimide (NMI) using a poly(N,N-dimethylacrylamide) (PDMAC) stabilizer as a soluble precursor. Conducting such PISA syntheses in a 50 : 50 w/w ethanol/methyl ethyl ketone (MEK) mixture leads directly to the formation of micrometer-sized PDMAC-P(St-alt-NMI) diblock copolymer particles at 20% w/w solids. Adjusting the degree of polymerization (DP) of the core-forming P(St-alt-NMI) block to target highly asymmetric copolymer compositions provides convenient access to an inverse bicontinuous phase. TEM studies of intermediate structures provide useful insights regarding the mechanism of formation of this phase. SEM studies indicate that the final copolymer particles comprise perforated surface layers and possess nanostructured interiors. In addition, control experiments using 1,4-dioxane suggest that the high chain mobility conferred by the MEK co-solvent is essential for the formation of such inverse bicontinuous structures. One-pot PISA formulations are reproducible and involve only cheap, commercially available starting materials, so they should be readily amenable to scale-up. This augurs well for the potential use of such nanostructured micrometer-sized particles as new organic opacifiers for paints and coatings.

Molecular simulations of coarse-grained diblock copolymers (DBP) were conducted to study the effect of segregation strength and morphology on transport properties. It was found that in the strong segregation limit (i.e., high χN, where χ is the Flory-Huggins parameter and N is the degree of polymerization), the presence of the DBP interfaces imposes topological constraints similar to those of entanglements as manifested in the rheological signature of the polymer (i.e., a plateau modulus). Furthermore, compared to the behavior of isotropic melts, the crossover from Rouse to reptation scaling of the self-diffusion coefficient (D) parallel to the DBP interface takes place at a smaller N, an effect that depends on temperature and is more pronounced in the Lamellae morphology than in the hexagonal cylinder morphology. Additionally, it is shown that for an entangled melt (i.e., N ≫ Ne where Ne is the entanglement length) block retraction is instrumental for chains to diffuse parallel to the interface of lamellar layers. Lastly, it is found that the anisotropic viscosity of different morphologies is mostly affected by the orientation of the chains relative to the shear flow direction, exhibiting reduced values when chains align in the neutral or flow directions.

A novel acrylate monomer 2-((3-(isopropylamino)-3-oxopropyl)(methyl)amino)ethyl acrylate (IMA) was synthesized by facile sequential two-step reactions and polymerized using reversible addition–fragmentation chain transfer (RAFT) polymerization to yield a thermo-, pH- and CO2-responsive homopolymer PIMA with a well-defined structure. PIMA showed a lower critical solution temperature (LCST) close to body temperature, and the influence of the degree of polymerization (DP), polymer concentration, salt concentration and substituents on the LCST was investigated. Due to the presence of tertiary amino groups in the side chains, the thermoresponsive phase transition of PIMA was tunable by solution pH and bubbling CO2/N2. The LCST increased with the decrease of pH, and the solubility of PIMA (at a temperature above the LCST) could be reversibly switched back by bubbling CO2/N2.

High molecular weight polyglycerol-dendronized poly(norbornene)s (PGD-PNBs) were prepared via ring-opening metathesis polymerization of norbornene monomers containing amine functional groups on the side-chains followed by dendron growth from the olefins of PNB backbones using iterative dihydroxylation and allylation. The fourth-generation PGD-PNB with a degree of polymerization of ca. 500 is thus functionalized with 16 peripheral hydroxyl groups as well as a single amine on each repeat unit of the PNB backbone. Furthermore, the amine functionality could be used to install hydrophobic fluorophores such as coumarin and pyrene, thereby obtaining the final PGD-PNB structures which are highly water-soluble and fluorescent.

We infer the swelling/de-swelling behavior of weakly ionizable poly(acrylic acid) (PAA) brushes of 2-39 kDa molar mass in the presence of KCl concentrations from 0.1-1000 mM, pH = 3, 7, and 9, and grafting densities σ = 0.12-2.15 chains per nm2 using a Quartz Crystal Microbalance with Dissipation (QCM-D), confirming and extending the work of Wu et al. to multiple chain lengths. At pH 7 and 9 (above the pKa ∼ 5), the brush initially swells at low KCl ionic strength (10 mM) in the "osmotic brush" regime, and de-swells at higher salt concentrations, in the "salted brush" regime, and is relatively unaffected at pH 3, below the pKa, as expected. At pH 7, at low and moderate grafting densities, our results in the high-salt "salted brush" regime (Cs10 mM salt) agree with the predicted scaling H ∼ Nσ+1/3Cs-1/3 of brush height H, while in the low-salt "osmotic brush" regime (Cs10 mM salt), we find H ∼ Nσ+1/3Cs+0.28-0.38, whose dependence on Cs agrees with scaling theory for this regime, but the dependence on σ strongly disagrees with it. The predicted linearity in the degree of polymerization N is confirmed. The new results partially confirm scaling theory and clarify where improved theories and additional data are needed.

Dilute dispersions of poly(lauryl methacrylate)–poly(benzyl methacrylate) (PLMA–PBzMA) diblock copolymer spheres (a.k.a. micelles) of differing mean particle diameter were mixed and thermally annealed at 150 °C to produce spherical nanoparticles of intermediate size. The two initial dispersions were prepared via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate in n-dodecane at 90 °C. Systematic variation of the mean degree of polymerization of the core-forming PBzMA block enabled control over the mean particle diameter: small-angle X-ray scattering (SAXS) analysis indicated that PLMA39–PBzMA97 and PLMA39–PBzMA294 formed well-defined, non-interacting spheres at 25 °C with core diameters of 21 ± 2 nm and 48 ± 5 nm, respectively. When heated separately, both types of nanoparticles regained their original dimensions during a 25–150–25 °C thermal cycle. However, the cores of the smaller nanoparticles became appreciably solvated when annealed at 150 °C, whereas the larger nanoparticles remained virtually non-solvated at this temperature. Moreover, heating caused a significant reduction in mean aggregation number for the PLMA39–PBzMA97 nanoparticles, suggesting their partial dissociation at 150 °C. Binary mixtures of PLMA39–PBzMA97 and PLMA39–PBzMA294 nanoparticles were then studied over a wide range of compositions. For example, annealing a 1.0% w/w equivolume binary mixture led to the formation of a single population of spheres of intermediate mean diameter (36 ± 4 nm). Thus we hypothesize that the individual PLMA39–PBzMA97 chains interact with the larger PLMA39–PBzMA294 nanoparticles to form the hybrid nanoparticles. Time-resolved SAXS studies confirm that the evolution in copolymer morphology occurs on relatively short time scales (within 20 min at 150 °C) and involves weakly anisotropic intermediate species. Moreover, weakly anisotropic nanoparticles can be obtained as a final copolymer morphology over a restricted range of compositions (e.g. for PLMA39–PBzMA97 volume fractions of 0.20–0.35) when heating dilute dispersions of such binary nanoparticle mixtures up to 150 °C. A mechanism involving both chain expulsion/insertion and micelle fusion/fission is proposed to account for these unexpected observations., Dilute dispersions of poly(lauryl methacrylate)-poly(benzyl methacrylate) diblock copolymer spheres of differing mean diameter are mixed and thermally annealed at 150 °C to produce either spherical or non-spherical nanoparticles of intermediate size.

The synthesis, characterization, and post-synthetic functionalization of a readily functionalized step-growth linear polymer derived from divinyl sulfone (DVS) and tert-butylcarbazate (TBC) is presented. Construction of this atom-economic polymer under thermal conditions proceeds in high yield (>94%) at 75 °C, achieving a number average molecular weight of 17.0 kDa, a weight-average molecular weight of 26.2 kDa, and a polydispersity of 1.54, corresponding to a number-average degree of polymerization >60, despite the step-growth nature of the reaction. Removal of the Boc-groups yields a polymeric scaffold with hydrazine moieties that are readily reacted with aldehydes to yield the corresponding functional polyhydrazone materials. A variety of hydrazone-linked functionalities are readily added under mild conditions, including cationic, anionic, electron-rich/poor, and hetereoatom-containing aromatics. Owing to its rapid functionalization and simple and scalable synthesis, this material is an accommodating and generalized polymer scaffold that is rapidly tailored to a variety of applications with easily introduced functionality.

Electrochemically mediated atom transfer radical polymerization (eATRP) of methyl acrylate (MA) was carried out for the first time in an ionic liquid, 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIm][OTf]). Ionic liquids are particularly suitable as solvents for eATRP because (i) a supporting electrolyte is not required, (ii) purification of the polymer is simple, and (iii) the catalyst can be recycled maintaining most of its original activity. Polymerization was relatively fast and well-controlled, affording polymers with a dispersity of ∼1.1 at >90% conversion in 2 h. Different conditions were explored, including applied potential, applied current, temperature, the monomer/solvent ratio, targeted degree of polymerization (from 276 to 828), and catalyst loading (down to 45 ppm). The livingness of MA polymerization was confirmed by realizing an electrochemical switch (ON/OFF toggling) and by the chain extension of poly(methyl acrylate)-Br with acrylonitrile. Chain extension was carried out for the first time by a “catalytic halogen exchange”, i.e. 180 ppm of a Cu complex was used to convert the chain end from C–Br to C–Cl. This afforded a well-controlled poly(methyl acrylate)-b-poly(acrylonitrile)-Cl copolymer.

We report the synthesis of zwitterionic homopolypeptides and block copolypeptides bearing carboxybetaine and sulfobetaine (CB and SB) via combining γ-propargyl-L-glutamate NCA polymerization with efficient Huisgen's click reaction. The zwitterionic homopolypeptides adopted versatile chain conformations upon varying the solution pH, depending on the chain length and functional group. The zwitterionic homopolypeptides with a degree of polymerization (DP) of 60 adopted stable α-helical conformation due to their elongated side-chain, whereas the short ones (DP = 20) adopted different conformations at varying solution pH. Their interactions with proteins depend on the chain conformation and zwitterionic group. The short one bearing SB exhibited very low interactions with lysozyme and myoglobin due to its coil and zwitterionic nature. A preliminary study showed that the zwitterionic block copolypeptides self-assemble to form vesicles with tunable molecular packing and solution behavior. These biodegradable/biocompatible, zwitterionic polypeptides may be promising materials in many applications such as non-fouling coatings and drug delivery.

FSG–PAN, an effective extractor, has been synthesized by chemically immobilizing PAN (1-{2-prydylazo}-2-naphthol) on silica-gel using an efficient silane-coupling-reagent, dimethyldichlorosilane. The corresponding luminescent nanomaterial has been utilized for the selective detection of Be(II) (LOD ≥ 0.75 × 10−6 mol L−1) amidst natural contaminants. The extractor selectively sorbed beryllium and aluminum (both as aqua-tri-nuclear-species, {Be3O(OH)2}2+ and {Al3(OH)3(H2O)2}6+), and uranium (as a bi-nuclear-aqua-species, {(UO2)2(OH)2(H2O)7}2+) at its highest occupied molecular orbital (HOMO) through HOMO : metal-ion-species 1 : 1 ion-pair formation. The binding stability of this interaction (0.012 eV mol−1/0.28 kcal mol−1) lies well below the classical bond energy (104 kcal mol−1) of any kind of chemical bond. The HOMO (μmol g−1) is thus an important quantitative part of the breakthrough capacity (BTC) and is expressed as BTC = {amount of HOMO (μmol g−1) × x}, where HOMO = 218 μmol g−1 and x = degree of polymerization; here, x = 3 for Be(II)/Al(III) and 2 for U(VI). Along with its excellently high BTC and enrichment factor (PF) (BTCBe(II): 645, BTCAl(III): 640, BTCU(VI): 428 μmol g−1; PFBe(II): 93.6, PFAl(III): 90.5, PFU(VI): 91.6), the appreciable durability (reusability ≥1000 cycles) and remarkable chemical inertness (BTC4M HNO3/H2SO4/HCl ≥ 95% at 4 mol L−1 acid-treatment) of the material signify its stability. By exploiting sorption-desorption selectivity, Be(II) has been sequentially separated (recovery ≥94.5 ± 2.5%) from several real and ‘synthetic multicomponent’ samples comprising its congeners.

Lewis acid–base chemistry has been demonstrated to be an effective strategy to adjust the optoelectronic properties of organic materials, especially conjugated small molecules. However, for conjugated polymers with large molecular weight, the stoichiometry of the Lewis acid–base reaction remains an interesting topic to research. In this work, two copolymers, namely P1 and P2, were synthesized, by covalently bonding two fused and co-planar units, i.e., indacenodithiophene (IDT) and indacenodithieno[3,2-b]thiophene (IDTT), respectively, with a pyrazine unit, a strong Lewis base containing two nitrogen (N) atoms within the heterocycle. The Lewis acid B(C6F5)3 (BCF) was selected to coordinate with the N atoms in the polymer backbone. The number-averaged degree of polymerization (DP) estimated from gel permeation chromatography (GPC) was found to be 16 and 14, respectively, for P1 and P2, indicating that the average number of coordination sites is 32 and 28, respectively, per chain of P1 and P2. Titration experiments conducted by gradually adding BCF to the polymer solutions revealed red-shifted absorption bands. The terminal of the titration was found upon the addition of 40 eq. and 32 eq. of BCF to P1 and P2 solutions, respectively. By adding excess BCF to fully coordinate with the N atoms, the optical bandgaps declined from 2.10 eV (P1) to 1.49 eV (P1/BCF) and from 2.08 eV (P2) to 1.32 eV (P2/BCF). Meanwhile, the LUMO levels estimated from electrochemistry experiments were also depressed from 3.60 eV (P1) to 3.96 eV (P1/BCF) and from 3.59 eV (P2) to 4.12 eV (P2/BCF). Electrostatic potential surface (EPS) maps deduced from Gaussian simulations revealed that electron density located on the polymer backbone was withdrawn by BCF, transforming the polymer skeleton from electron rich to electron deficient. This revealed the reason for the decrease in the bandgaps and the reduction of the energy levels upon coordination with BCF.